Menopause has been associated with changes in body composition and increased cardiovascular risk factors in Caucasian women, although less information is available on the effects of menopause in African- American women. Changing levels of reproductive hormones are central to the physiological changes at menopause and, since these hormones have been related to body fat distribution, its likely that they play a role in body fat-related changes at this time of life. The overall goal of this proposal is to assess the influence of menopause on body composition and fat distribution, and to determine mechanisms they may influence body fat changes, in a prospectively followed cohort of Caucasian and African-American women. the studies outlined will address 4 general hypotheses. First, we hypothesize that menopause increases both total and visceral abdominal fat. Second, we hypothesize that the changes in body composition and body weight at menopause are mediated, at least in part by changes in 24-hour energy expenditure, physical activity and/or food intake. Third, we hypothesize that menopause results in decreased insulin sensitivity that may predispose certain women to develop diabetes later in life. These changes in insulin action may be connected to changing adiposity or may be independently related to hormonal changes. finally, we hypothesize that there may be a differential responsiveness to menopausal changes in African-American women, who end to have differences inn adioposity, insulin sensitivity, and reproductive hormone levels premenopausally compared to Caucasian women. Since health statistics for African-american women are significantly worse than for the U.S. Caucasian population, understanding the effects of menopause on risk factors in african-American women is of great public health significance. In order to address these hypotheses related to the effects of menopause, a longtidudinal study is proposed where premenopausal women aged 47-52 year old will be assessed annually and changes in outcome variables in relation to aging and menopausal status will be determined. Major outcome variables include intra-abdominal far distribution by CT scan, body composition, 24-hr energy expenditure, food intake and activity, and insulin sensitivity by the Minimal Model method. Among the strengths of this design include the ability to address mechanisms of menopausal changes since sequential measurements will be taken over time in these outcome variables. The importance of this research was underscored in a recent consensus report from the National Institute on Ageing stating that "The need for longitudinal (observations) of women over time ... is essential ... to advance our knowledge of the natural history of menopause".